I would disagree with somebody sucker-punching a community member in the face. If there are no other targets this seems entirely legitimate.
The ban also seems slightly prejudicial, because on the other side there is /r/antifa where people are bragging[1] about the assault which /r/altright was trying to solve with this bounty. Granted, /r/antifa seems to be mostly dissent against this stuff, so it wouldn't be a subreddit shutdown.
I think that assaulting people you disagree with is a far more serious charge than posting a reward for information which leads to the arrest of a criminal. The latter is something befitting of a police agency.